An expansion anchor of the generic type is disclosed, for example, in European patent application EP 0 514 342 A1. Such an anchor is used to anchor components in a hole drilled in a solid substrate, for example, in concrete. The prior-art expansion anchor has an elongated stud whose front end has a conical expanding section that widens counter to the pull-out direction. Offset relative to the expanding section, there is an expansion sleeve that is mounted so as to be movable counter to the pull-out direction. The expansion sleeve has elevations on the outside which protrude in the radial direction and with which the expansion sleeve can dig into the inner wall of the hole drilled in the substrate. The expansion anchor, with the expansion section facing forward, is hammered into the drilled hole counter to the pull-out direction, and subsequently, the stud is once again pulled somewhat out of the drilled hole in the pull-out direction. Once the expansion anchor has been hammered in, the expansion sleeve digs into the inner wall of the drilled hole, as a result of which it is held back in the drilled hole when the stud is pulled out. Consequently, the expanding section of the stud is pulled into the expansion sleeve, a process in which, due to the increasing diameter of the expanding section, the expansion sleeve is widened and the expansion anchor with its expansion sleeve is clamped in the substrate so that loads can be transferred into the substrate. This basic principle can preferably be implemented in the invention as well.
In order to ensure a reliable widening of the expansion anchor, movements of the expansion sleeve when the stud is initially pulled out should be prevented. For this purpose, according to European patent application EP 0 514 342 A1, elevations are provided on the expansion sleeve which affix the sleeve after the expansion anchor has been hammered into the drilled hole. However, the larger these elevations are, the more difficult it can be to hammer the anchor into the drilled hole. Consequently, the holding force that can be achieved with elevations often means that a compromise has to be accepted when it comes to the behavior of the anchor when it is being hammered in.
European patent application EP 0 167 481 A1 describes an expansion anchor which can be anchored in a substrate under axial pre-tensioning and with which a counter-bearing is tensioned against the substrate, whereby, between the counter-bearing and the substrate, there is a can-like container that can be extended along the longitudinal axis of the anchor and that has a cavity for a swellable compound. When this compound swells up, it can then maintain the pre-tensioning of the anchor.